1. Field of the Invention
The invention is directed to a method of preparing inorganic oxide aerogels and, in particular, inorganic oxide aerogels in the form of granular material characterized by high surface area and pore volume.
2. Relevant Art
Inorganic oxide aerogels, specifically metal oxide aerogels, are well known in the art as suitable for a variety of applications such as catalysts, catalyst supports, absorbents, chromatographic column packing, anticaking agents, viscosity enhancers, pigments, opacifiers, as well as ceramics, smoke suppressants, abrasives, dentifrice polishing agents and the like.
Examples of some known prior processes wherein the aerogels prepared in the manner disclosed are utilized as catalysts or catalyst supports are as absorbents in preparing solid phosphoric acid catalysts (as disclosed in U.S. Pat. No. 3,673,111); as a catalyst support for rhodium in the production of olefins and long chained hydrocarbons as is discussed in the Journal of Molecular Catalysis, Volume 17, pgs. 219-223 (1983); in the hydrocarbon synthesis from CO and H.sub.2 disclosed in U.S. Pat. No. 4,273,724; in the Fischer-Tropsch synthesis described in Journal of Molecular Catalysis, Vol. 17 (1982), pgs. 171-181; as support for catalyst used in the manufacture of phthalic anhydride; and as a catalyst in the decomposition of hydrogen peroxide.
The preparation of aerogels, in general, and silica aerogels, in particular, has been well documented in the art. U.S. Patent Nos. 2,249,767, 3,672,833, 2,093,454 and 4,327,065 all disclose processes for producing aerogels. In addition, an article entitled Inorganic Oxide Aerogels appearing in Advances in Colloid and Interface Chemistry, Vol. 5, pages 245-273 (1976) published by Elsevier Scientific Publishing Co., Amsterdam, also describes methods of producing various aerogels.
It has been known to produce such aerogels by hydrolyzing salts, or alkoxides, in the presence or absence of a catalyst, generally an acid or base, to form a gel which is washed with water and then solvent exchanged with an alcohol prior to conventionally drying in an autoclave at the critical temperature and pressure of the solvent.